1. Field of the Invention
According to a first aspect, the present invention relates to truck-mounted breakers intended for high-voltage lines. According to a second aspect, the invention relates to a method of supporting electrical counterpart contact units in a breaker. By high-voltage line is normally meant a line for voltages above 72.5 Kv, and shall be interpreted as such in this Application.
2. Discussion of the Background
A truck-mounted breaker, so-called truck breakers of the kind with which the invention is concerned, connects and disconnects part of the electric circuit, by moving the electric contact devices carried by the truck breaker into and out of engagement with corresponding, stationarily mounted counterpart contact devices, wherewith the contact devices are preferably moved linearly on a pair of stand-mounted rails. This results in an insulation gap (air gap) on each side of the breaker, which corresponds to opening a disconnector on each side of the breaker. The counterpart contact units of the counterpart contact device are normally mounted in a top and a bottom row, of which the bottom row is normally supported by insulators that are mounted directly on the stand, and which also support the linearly movable contact device, therewith guaranteeing a good fit between the bottom contact units and the counter-contact units. The countercontact units in the upper row are normally held up by insulators depending from a portal. A portal is anchored on a plinth that is separate from a concrete plinth of the stand that supports the linearly displaceable contact device. Consequently, there is a risk that these upper countercontact units will not be retained in a correct position for receiving corresponding electrical contact units on the displaceable contact device. This is because the position of the portal relative to the position of the stand carrying the electrical contact device being disturbed by the thawing of frozen ground, earthquakes or other soil or earth disturbances. Such misalignment may make it impossible to mutually connect the upper contact units with the counter-contact units.
Truck breakers for low and intermediate voltage problems are not confronted with this problem, since in these cases the counter-contacts can be mounted on horizontal beams, one for each vertically distributed group of counter-contact units, as disclosed in DE 1 415 613, for instance. This is made possible by virtue of the short insulation paths that are required in such cases, so as to enable each counter-contact to be attached to the stand with a short insulation element. However, it is not possible to scale-up such a construction for high-voltages, since the pin insulators then become longer and result in an unacceptably high building structure if requisite safety distances are to be maintained.